Wet Ox uniformity issues

Folks,
As some of you might know, we have be tracking down wet oxidation
non-uniformity in tylan4. All the data is in the equipment archinve for
tylan4 on line, but the quick summary is that wafer-to-wafer uniformity
has been as bad as 30% with within-a-wafer uniformity at about 22%.
Earlier this week two tests revealed the uniformity has drastically
improved to 4% wafer-to-wafer and 2% within-a-wafer. Based on these
results we are sending out this message to warn users of tylan4 about
possible inconsistencies affecting wet oxidations in this tube.
Dry oxidations are fine.
If you choose to use this furnace for wet oxides and notice gross
non-uniformities please let us know. Our efforts to chase this problem
down have led to more puzzlement than enlightenment.
Thanks for your attention to this,
Team Furnace
--
Nancy Latta
Stanford Nanofabrication Facility
CIS Room 145
420 Via Palou Mall
Stanford, CA 94305-4070
(650) 725-6727
latta at snf.stanford.edu